Electric telephone



(No Model.) 2 Sheets-Sheet l.

lJ. P. FREEMAN. ELECTRIC-TELEPHONE.

1510.262285.' Patented Aug, 8, 1882.

(No Model.) 2 Sheets--Sheet. J. P. FREEMAN.

ELECTRIC TELEPHONE. No. 262,285. Patented Aug. 8, v1882.

L MW ff? www? UNITED STATES PATENT Ormea.

' JAMES P. FREEMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE HOME TELE- PHONE COMPANY, OF ILLINOIS.

ELECTRIC TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 262,285, dated August 8, 1882.

Application filed September 24, 1881.

To all whom it may concern Be it known that I, JAMES l". FREEMAN, a citizen of the United States, residing at Ghicago, in the county ofOook and State ot'Illinois, have invented ce1 tain new and useful Improvementsin Electric Telephones; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference.

being had to the accompanying drawings, and to the letters or figures of reference marked thereon, which form a part of this specification.

Thisinvention relates to electric telephones adapted to the transmission and reproduction of articulate speech by means of electrical waves or impulses traversing a circuit.

My improvement concerns more particularly telephonic transmitters; and it consists principally of the combination of a mainspring for primarily holdingthe electrodes in contact with each other and one of them in contact with the diaphragm, and two compensating-springs for regulating the pressure with which the electrodes bear on each other and on the diaphragm. This combination of springs affords the means for ready and delicate adjustment of the electrodes with reference to each other and to the diaphragm, so thatthe instrument can be made exceedingly sensitive to sound-vibrations.

In order that my invention may be clearly understood, I have illustrated in the annexed drawings and will proceed to describe the best form thereof at present known to me, and which I practically tested and found very et'- fective.

In the annexed drawings, Figure l is a perspective view of so much of the telephonie transmitteras will illustrate myinvention. Fig. 2 is a plan View. Fig. 3 is a cross-section on line :c x of Fig. 2. Fig. 4 is a sectional view of the well-known form of metallic diaphragm, which may be used in lieu of the wooden diaphragm seen more particularly in Fig. 3.

The same letters of reference indicate like parts in all the gures.

The various mechanical devices used in the construction of my invention are mounted on (No model.)

shown in Fig. 3, or the ordinary metallic diaphragm applied in the ordinary way, as shown in Fig. 4. The vibrations of this diaphragm are transmitted by the electrode C, in contact therewith, to the electrode I), the ordinary 6o carbon button acting in a well-known manner. The electrode C, preferably a stem of platinum, is secured to the free end of an arm, E, on the shaft E', which is pivoted between center screws E2 E2 on a base-plate, E3, secured to 65 the inside ofthe door A. The electrode D is fixed to the free end of an arm, F, of a shaft, y F', pivoted between center screws F2 F2 on a base-plate, F3, secured to theinside ofthe door. The shafts E' and F are in this instance ar- 7o ranged parallel with each other on opposite sides of the center opening in the door, and their position with reference to the diaphragm and to each other is such that the electrode C may touch with one end the center of the diaphragm and the center of the carbon button with the other end.

The arms E and F may be of unequal length, as shown. The arm F is provided with al hook, j', (on about the radial line of the shaft FQ) to 8o which one end of the spiral mainspring G is hooked. The other end of this mainspring is' connected by a thread,g, to the stem of a button, e', frictionally secured in the eye of a projection, e, formed on arm E. Ihus the mainspring G tends to turn the arms E and F so as' to force the electrode C against the diaphragm and the electrode D against the electrode O. The tension of the mainspring should be properly adjusted above the point giving 9o the required approximate pressure to be exerted bythe electrodes on each other and on the diaphragm. This approximate primary adjustment of the mainspring can be readily effected by winding or unwinding the thread g by the turning of the button g'.

In order to adjust the pressure with which the electrode C touches the diaphragm in conto prevent it from warping, and applied as 55A sequence of thc action of the niainspring g', a spiral com pensating-spring, H, is used, hooked with one end around the stem of the button e', and connected by athread, h, to the stem of the button H', frictionally secured in the socket'h, xed on the door A. By properly adjustingthis compensating-spring H the pressure of the touch of the electrode C on the diaphragm may be very delicately adjusted without affecting the tension ot' the mainspring to any perceptible degree. For adjusting the pressure of the electrode D on the electrode C al similar spiral compcnsating-spring, I, is attached to the hook j", and connected by a thread, t', to the stem of' abutton, l', frictionally secured in a socket, t", fixed to the inside ot' the door A. The action of the eompensating-springs is necessarily opposed to that ofthe mainspring, and in such a way that their tension is relaxed every time the diaphragm moves inwardly, so that the pressure of the electrodes upon each other is increased not only by the stretching ofthe mainspring, but also in consequence ot the decreased opposing action of the compensating-springs.

The arm E is electrically connected by wire l and other metallic conductors to one pole of the battery, while the arm F is connected by the action ot the mainspring.

2. The combination, substantially as before set forth, ofthe diaphragm, the electrodes, two pivoted arms supporting the electrodes, the mainspring acting on both said arms for torcing` one electrode against the other and the latter against the diaphragm, and a compensating-spring for each arm for modifying the ac tion of the mainspring.

ln testimony whereof I attix my signaturein presence ot' two witnesses.

JAMES I. FREEMAN.

Witnesses:

OHAs. S. HYER., C. A. NEALE. 

